A hammertoe, or contracted toe, is a deformity of the proximal inter-phalangeal joint of the second, third, or fourth toe causing the toe to be permanently bent and giving the toe a semblance of a hammer. Initially, hammertoes are flexible and may be corrected with simple measures but, if left untreated, hammertoes may require surgical intervention for correction. Persons with hammertoe may also have corns or calluses on the top of the middle joint of the toe or on the tip of the toe and may feel pain in their toes or feet while having difficulty finding comfortable shoes.
One method of treatment may include correction by surgery if other non-invasive treatment options fail. Conventional surgery usually involves inserting screws, wires or other similar implants in toes to straighten them. Traditional surgical methods generally include the use of Kirschner wires (K-wires). K-wires require pings protruding through the end of respective toes due to their temporary nature. As a result, K-wires often lead to pin tract infections, loss of fixation, and other conditions. Additional disadvantages of K-wires include migration and breakage of the K-wires thus resulting in multiple surgeries. Due to the various disadvantages of using K-wires, however, compression screws are being employed as an implant alternative.
Screw implants may provide a more permanent solution than K-wires as such implants do not need removal and have no protruding ends. Further, with the use of screw implants, a patient may wear normal footwear shortly after the respective surgery. There are generally two types of known screw implants: single-unit implants, which possess a completely threaded body and do not provide a flexibility to the respective toe in its movement, and articulated or two-unit implants, which typically have one unit that is anchored into the proximal phalanx, a second unit that is anchored into the distal phalanx, and a fitting by which the two units are coupled. Either or both of the two units may be threaded or have other anchoring structures such as barbs or splaying arms.
Among other disadvantages, both kinds of known implants result in an undesirable pistoning effect, i.e., part or all of the implant will toggle or move within the bone as the patient's toe moves. Pistoning decreases the stability of the implant and lessens the compression across the joint. Moving parts, such as fittings, hinges, expansion pieces, and the like also decrease the stability, lifespan, and compression force of the implant. Accordingly, there remains a need for durable hammertoe implants which are not only stable but provide adequate compression across a joint with minimal pistoning. There also remains a need for an implant which can provide these advantages, while being easily inserted with minimal damage to the surrounding tissue.